1. Field of the Invention
The present invention relates to acoustic line arrays and more particularly to a long, continuous, constant diameter neutrally buoyant, pliable plastic hose, towed array without couplings having strength members and electrical conductors embedded within and between the hose wall materials.
2. Description of the Prior Art
Oceanographic, engineering and acoustic data are presently gathered in the seas by towing arrays of sensors, placed within a long string of reinforced pliable plastic oil filled hose sections. The oil is very light and serves the double function of providing electrical insulation and neutral buoyancy. This assembly of sections, comprising a towed array, can be as long as several thousand feet and vary in diameter from less than one inch up to four inches, depending on the sensor requirements. From an acoustic standpoint, a constant diameter array is preferred in order to minimize flow noise.
Existing towed arrays terminate the strength members and electrical conductors in sectional end couplings, which occur at least every 300 feet. Long fabrication areas are required because in order to place sensors within the hose cavity, the hose must be expanded. This is accomplished by placing a hose section inside a 300 foot long vacuum chamber and pulling a vacuum on the outside of the hose. The strength members, conductors and sensors are assembled on the top of long benches, normally placed next to the vacuum chamber. The strength members are tensioned and the other elements are tied on. Next the assembled conductors, sensors and strength members are pulled into the hose section. Finally the couplings are attached to the hose section ends and sealed, and the hose section is filled with the lightweight oil. A plurality of such assembly of hose sections are assembled and connected end to end to construct a towed array which may be several thousand feet long.
Each mechanical and electrical coupling represents a potentially unreliable piece of hardware. They are relatively heavy compared to the other array components, being typically made of metal such as titanium, and are very expensive to machine. In addition, highly skilled personnel are required for the difficult and tedious task of terminating the strength members at each coupling. The electrical connectors are of necessity normally small in diameter resulting in the pins being placed very close together. This leads to potentially serious safety problems when high voltages are used during array operation. Also, since the couplings are heavy, local sagging occurs at each coupling while the array is being towed. This dip in an otherwise neutral, horizontal array produces flow separation resulting in flow noise which causes a reduction in the acoustic performance of the array. There is also evidence that the couplings act as shiny lures for fish to attack which also degrades array linearity.